1. Vergilius Maro, P.: Aeneid, (Book VI Stanza LVI
2. Abramowitz, M., Stegun, I.A., Handbook of mathematical functions, (Dover 1965)
3. Wilson, M.: American science and invention: a pictorial history, (Bonanza Books, New York 1960)
4. Special issue ofScience(journal of the AAAS), 30th Jan. 1970,167, (3918)